The use of power amplifiers in transmitting radio frequencies (RF) signals has many applications, including but not limited to wireless communications systems. In digital cellular communication systems, such as time division multiple access (TDMA) communications systems, wireless terminals may share a single wireless communication channel (e.g., shared frequencies) on which they broadcast. Each wireless terminal that shares a channel may be allocated a time slot on a repetitive basis. During this time slot, the wireless terminal ramps up its power amplifier to a predetermined frequency and power, sends the desired information, and at the end of the time slot, ramps down the power amplifier so as not to disturb or interfere with other wireless terminals sharing the same frequency. This ramping up and ramping down of output power defines a power profile.
Some wireless communication standards define the power profile that is to be used by wireless terminals. For example, FIG. 1 illustrates a power profile of transmission power versus time for the GSM (Global System for Mobile Communications) communication protocol. See 3rd Generation Partnership Project; Technical Specification Group GERAN; Digital cellular telecommunications system (Phase 2+); Radio transmission and reception (Release 1999), document 3GPP TS 05.05 V8 6.0 (2000-09), Annex B (normative. Transmitted power level versus time). The power profile that is illustrated in FIG. 1 includes a ramp up portion, a full power portion, and a ramp down portion.
In a TDMA digital communications systems, if a wireless terminal ramps its transmitted power up or down too slowly, information may not be properly transmitted or received within an assigned slot, and/or the transmitted information may improperly extend into an adjacent slot. In contrast, if a wireless terminal ramps up or down its transmitted power too quickly, unacceptably large spectrum widening may result that can interfere with other wireless terminals using adjacent or alternate frequencies. Therefore, a wireless terminal should change its transmission power quickly and smoothly without causing an unacceptable spectrum widening, interference, and/or loss of transmitted information.